1. Field of the Invention
The present invention relates to a stochastic processor based on a novel operation principle. More particularly, the present invention relates to a stochastic processor capable of operating vector matching as an essential operation in a recognition process at high speeds, and a recognition process device using the same.
2. Description of the Related Art
With recent spread of personal computers (PCs), processors have been increasingly used at home. In addition to numeric value calculation, personal uses such as Internet, mail, and image processing have been increasing.
However, in the PCs capable of high-speed operations, sufficient speeds are not achieved in all the operations. For example, in order to recognize a voice or speech given off by a person or recognize who a person being viewed through a camera is, enormous amount of operations are required to perform, and therefore, real time processing is difficult.
Basic operation of such recognition process is to store data of a voice or face in vector form, vectorize input data in the same manner and detect approximation between these data, and perform operation as to which of the reference vectors is closest to the input vector. Such vector comparison process is a basic process used in wide variety of data processing such as associative memory, vector quantization, and pattern recognition such as motion prediction, and data compression.
Such vector comparison requires enormous amount of operations in any of the applications. In Neuman-type computers which are typical of the conventional PCs, in principle, the closest vector cannot be extracted unless comparison operations of all the vectors are finished. As a result, very long time is required.
On the other hand, human beings can perform these recognition processes without any difficulty. So, it becomes necessary to compensate for the conventional computers by carrying out these processes at high speeds in selected computers with operation principle different from those of the conventional computers.
One example of the processor based on such a new operation principle is disclosed in Japanese Laid-Open Patent Application Publication No. Hei. 2001-313386, entitled “data processing structure.”
FIG. 40 is a perspective view schematically showing a structure of the conventional processor. As shown in FIG. 40, in the conventional processor 220, a power electrode 214 is disposed as opposed to a gate electrode 212 of a minute MISEFT 211, and a plurality of quantum dots 213 and 221 with the magnitude of a nanometer scale are provided between the electrodes 213 and 221. Specifically, a pair of data electrodes 222 are arranged at constant pitch in a width-wise direction of the gate electrode 212 (in a gate width direction), and the quantum dots 221 are arranged in a line shape between the each pair of the data electrodes 222. Reference numeral 301 denotes a virtual plane on which the data electrodes 222 and the quantum dots 221 are arranged. Between the quantum dots 221 arranged in the line shape and the gate electrode 212, the quantum dots 213 are arranged. Thereby, there is an energy barrier between the quantum dots 221 and the gate electrode 212, through which electrons can tunnel.
FIGS. 41A and 41B are schematic views showing an operation principle of the conventional processor 220 by using an equivalent circuit.
Referring to FIGS. 41A and 41B, voltages corresponding to an input pattern (input vector) and a reference pattern (reference vector) are input to each pair of data electrodes 222. These voltages are digital voltages each of which takes a voltage of binary value of 1 or 0. Upon these voltages being input to the each pair of data electrodes 222 with the quantum dots 221 disposed between them, electrons stay in the vicinity of the center by potentials determined by the each pair of data electrodes 222 (see FIG. 41A) or move (see FIG. 41B), which occurs stochastically, thereby causing a drain current of MISFET (Metal Insulator Field Effect Transistor) to vary.
By continuing to monitor the drain current, probability improves with lapse of time. Thereby, a solution close to a strict operation result is gained.
However, the conventional processor 220 has problems. First, because of the use of the quantum dots 213 and 221, it is necessary to wait establishment of a fabrication process of the quantum dots 213 and 221. This is burdensome because there arises a need for a technology other than a current semiconductor process technology.
In addition, comparison is made for so-called binary data in vector comparison. This is effective in obtaining a hamming distance but presents difficulty in calculating a Manhattan distance (absolute value of difference) for frequent use in actual data processing.
In the conventional processor 220, the voltages corresponding to elements of two vectors (input vector and reference vector) to be compared, are input to the each pair of data electrodes 222, where operation for obtaining difference between the elements is carried out in analog and stochastically. A sum of differences between the elements appears as the drain current of the MISFET 211. And, based on the magnitude of the drain current, difference between the two vectors, i.e., degree of approximation is judged. This is problematic, because it becomes necessary to detect the drain current with higher precision with an increase in the number of elements of vectors to be compared. Consequently, it becomes difficult to judge degree of approximation.